Generally, an emerging use of wide-band communication systems employing extremely high frequency Ka or V frequency bands is leading to development and implementation of commercial satellite systems which support a large number of high-gain spot beams. Because of high reuse of the available frequency spectrum, spot beam technology advantageously allows high capacity systems to be realized with a finite number of beams. For example, the primary frequency spectrum of the orbit slot is typically divided up equally among several spot beams to form a frequency reuse cluster, e.g., four beams per cluster. Spot beam technology also permits reduction of ground terminal size to a point where such terminals become commercially feasible as a mass-market end-user terminal.
In known payload designs for multi-beam systems, total capacity of the satellite is generally divided and allocated among the beams on a preferably equal basis so as to accommodate design simplification and cost reductions as well as changes in user demand and market needs. As a result, such payloads achieve maximum total throughput only when used in support of point-to-point (PTP) transmissions having an even traffic distribution among the respective beams at their individual full capacities. However, such even distribution is inherently unrealistic because certain geographic areas naturally have a higher use demand than others. In addition, changing market conditions and other networking factors directly impact the distribution of a system's traffic load. Thus, known multi-beam systems operate with a significantly reduced effective utilization of the satellite capacity when compared to the capacity with which the beams could otherwise collectively support.
Another drawback to known multi-beam systems and payload designs which are inherently suited for PTP transmissions is the loss of throughput efficiency when such systems are used to support broadcast transmissions to be sent to the entire geographic service area. Typically, such systems can only provide broadcast capability if the desired broadcast information is individually transmitted on every spot beam in the system.